Tuning mechanism for radio receivers



Sept. 15, 1942. A. W/PLENSLER 2,295,966

TUNING MECHANISM FOR RADIO RECEIVERS Filed March 8, 1938 2 Sheets-Sheet 1 Sept. 15, 1942.. A. w. PLENSLER TUNING MECHANISM FOR RADIO RECEIVERS 2 Sheets-Sheet 2 Filed March 8, 1938 Patented Sept. 15, 1942 TUNING MECHANISM FOR RADIO aaomvans Alexander W. Plensler, Chicago. 111., assignor to 7 Belmont Radio Corporation, Chicago, 111., a corporation of Illinois Application March a, 1938, Serial No. 194,634

3 Claims. (01. 74-10) This invention relates to tuning devices of the type commonly known as automatic tuning devices inwhich the pressing of a button automatically tunes a radio receiving set to the desired frequency corresponding to the station for which the button is marked. More particularly, the invention relates to automatic tuning devices -of a mechanical nature in which the force applied to the button supplies the rotative force for tumingthe tuning condensers. l

Quite a. few automatic mechanical tuningdevices have been proposed and one which has been found to be satisfactory is the type disclosed in one of applicants prior copending applications, in which a heart-shape cam is preset by holding it in its actuated position by pressing. a roller against it and rotating the tuning condensers to tune in a particular station so that the set may subsequently always be tuned to that station by pressing the roller against the heart-shape cam. .In all such tuning devices there are various problems to be solved, particularly the problem of providing dependability and ease of operation with a simple and inexpensive structure.

This problem was quite satisfactorily solved by my copending application mentioned. The pres- -ent. application is concerned with inventions.

which comprise further satisfactory solutions of this problem. 1

According to the present invention a push button which has a simple straight actuating movement similar to that of ordinary electric switch push buttons, but a little longer, is provided with an actuator having a pair of spaced laterally extending arms which engage a member mounted on a rotary shaft and having portions extending laterally from the shaft. The rotary shaft is connected to the tuning condenser and such member is moved by the arms of the actuator to a predetermined tuning position. The spaced arms of the actuator are preferably gu ded by a mally will not be satisfactory for rotating the shaft a full 180", and the rotary shaft will usually be geared to the condensershaft in approximately a 4 to 1 ratio so that a 45 movement of the first shaft, which may be called the countershaft, is enough to rotate the condenser shaft The objects of the invention are for the most part apparent from the foregoing discussion, but

from the following description drawings, in which:

Fig. 1 isa fragmentary plan view of one form and from the of the invention chosen for illustration.

-ing the parts with the Fig. 2 is asectional view taken approximately on the line 2-2 of Fig. 1. Fig. 3 is a similar but fragmentary view showactuator in released positlon.

Figs. 4 and 5 are fragmentary views corre-- sponding to Fig.2 but showing a modified form of the invention in extreme positions.

Figs. 6 and "l are fragmentary views corresponding to Fig. 4 but showing another modified form of the invention.

All of the forms of the-invention chosen for illustration are shown in conjunction 'with a tuning condenser havinga fixed frame ii and a rotatable shaft I2, which must be turned through 180 to provide the full range of tuning. The condenser, or in reality the bank of condensers, carried by the frame I I may be appropriately connected into a radio receiving set. In the form of the invention shown in Figs. 1 and 2 the shaft l2 carries a pinion l3 which meshes with a gear segment I4 by which the condenser is turned to tune the receiving set to a given frequency. The gear segment I4 is carried by a countershaft It to which it is keyed, the countershaft being journaled bythe support plates I1 and being rotated by push buttons I8 in a manner to be described.

The shaft l6 also carries a plurality of rocker arms or control members 2|, one for each key i8. These rocker arms are normally held in fixed relationship tothe shaft by friction means including washers 22 which are keyed to shaft I6 and clamped against the rockers 2| by means of spacing collars or bushings 23 and 24. The clamping force, may be exerted on the bushings 23 and 24 and washers 22, and hence on the rockers 2i simultaneously in any suitable manner as by letting the bushings bear against a screw 26 at one end of the shaft and screwing a thumb screw 21 on'the other end of the shaft. Suitable clamping means are also more fullydescribed in the copending applications noted above. The thumb screw 21 obviously clamps all of the bushings together and against the screw 26. When the thumb screw 21 is loosened, the rockers 2 [may be adjusted independently to different positions on the shaft l6 so that they may be used to tune the receiving set to different stafurther objects and advantages will be evident :5 tions. Sufficient pressure is maintained to hold the rockers temporarily in any position by a spring washer 28 and the support plates I1.

Each of the push buttons I8 is carried by an actuator 29 which includes the two legs 3|, on each of which is formed a pressure arm 32 positioned to engage the arms of the rocker 2| at widely spaced points. pressed, its arms 32 will shift the associated rocker 2| to the vertical position as shown in Fig. 2. If the rocker 2| were initially inclined in one direction as seen in Fig. 3, the upper arm 32 would strike it first, while if it were initially inclined in the other direction the lower arm would strike it first. Whichever arm strikes the rocker 2| first will rotate the .rocker 2| until the other arm 32'strikes the rocker 2|, to prevent further rotation of the rocker 2|. This will of course prevent the button I8 from being pressed in further and when the finger is released from button I8, it and the actuator 29 will be returned to the original position by a return spring 33. a A rubber collar or felt washer .34 may be provided on shank 29 to form a cushion between the enlarged inner end of actuator 29 and the frame 38 through which the actuator 29 slides and to which the return spring 33 is secured.

From the foregoing it will be seen that depressing a push button I8 will accurately position the corresponding rocker 2| provided that the actuator 29 is adequately guided. According to the present invention it is guided in a very accurate and simple manner by passing its legs, which areformed by its bifurcation, through a groove 38 in the bushing 23. This not only maintains the actuator 29 in proper vertical position with respect to shaft l8 but also maintains it in the proper longitudinal position along the shaftI8 with respect to the rocker 2 I. The button-carrying shank of actuator 29 should slide snugly in frame 38 or be biased against pivoting about shaft I8 by spring 33. In view -of this accurate guiding of the actuator 29 we may be sure that if I a rocker 2| is properly preset on the shaft I8,

depressing the corresponding button I8 willaccurately tune in the desired station.

To preset the rocker 2| on the shaft I8 for tuning in a given station, the thumb screw 21 is first loosened and the button I8 corresponding to the rocker2| to be adjusted is depressed to bring the rocker 2| to its actuated position shown in Fig. 2. The shaft I2 is then turned manually in any suitable mannerjas by manipulation of a knob 39 keyed to an extension of shaft I2 to tune the receiving set to the desired station. The button I8 may then be released and, unless other rockers 2| are to be similarly preset, the thumb screw 21 may be tightened to look all of the rockers 2| in fixed position on the shaft I6. Depressing the same button I8 will thereafter always return the same rocker 2| to its actuated 'position and hence tune the receiving set to the same desired station.

Although the arms 32 have been shown as simple lugs bent from the legs 3|, they could be formed by antifriction rollers secured to the legs 3| if preferred.

In Figs. 4 and 5 a modified form of the invention is illustrated in which the shaft 5| carrying the rockers 52 could have an operating angle of approximately 88 instead of approximately 45 as in Figs. 1 and 2. With an operating angle of 88 the shaft 5| could be geared to the condenser shaft I2 with a ratio of slightly over 2 to 1 instead of 4 to 1. In this form of the invention the rocker 52 has been provided with When the key. I8 is de-.

antifriction rollers 53 at each end thereof and the slide 54 is provided with a special pressure plate 58 which slopes to a point 51 at its center. In the latter half of the stroke of button I8 (Fig. 5) the action will be substantially the same as in Figs. 1 and 2. In the first half of the stroke, however, if one of the rollers 53 is turned nearly to a central position as shown in Fig. 4 the point 57 will strike said roller and thrust it away from the center position to a point where one of the extended arm portions of plate 58'may be effective to press the roller 53 until the other arm of plate 58 strikes the other roller 53.

Figs. 6 and 7 show still another modification of the invention which has the advantage of independence between the button assembly and the actuating assembly. With this form of the invention the button 8| can be mounted directly inthe cabinet wall 82, being retained therein by a head on one end and a c-washer 88 snapped in a groove on the other end. The button 8| presses against an actuator bar 88 which may be pivoted at 88 preferably to some structure which is independent of the chassis so that the chassis may be removed from the cabinet 82 separately. The actuator 84 may be drawn to its inactiveposition by a return spring 81 which presses the button 8I' to its inactive position also. The actuator 88 has two portions on opposite sides of its point of contact with button 8|, which portions engage the rocker 88 which may be very similar in its mounting and its associated parts to rocker 2|, although the angle of rocking may be a little larger. Whenever a push button 8| is pressed, it will press the actuator 88 against one end of the rocker 88 and this end of the rocker 68 will be pressed rearwardly until parts come to rest at the position shown in Fig. 'l. The use of the pivoted actuator 88 avoids all danger of irregularity in automatic tuning due to loose fitting of the actuator in sliding guideways. It will be understood, of course, that in both the structure of Figs. 4 and 5 and the structure of Figs. 6 and '7 there will normally be a plurality of rockers with a separate push button for each and trative and the invention is not to be limitedby them. In fact, if modifications or improvementsare not at once obvious, they may be devised in the course of time to make additional use of the broad ideas taught and covered by this application. The claims are intended to point out novel features and not to limit the invention except as may be required by prior art.

I claim:

1. Automatic tuning apparatus including a shaft adapted to drivea tuning device, a rocker on the shaft extending in two directions therefrom, an actuator having spaced arm portions adapted to engage the two extending portions of the rocker and to actuate it always to the same position to turn the shaft to a position corresponding with the position of the rocker on the place, said bushing member being grooved and receiving said supporting portion in guiding engagement therewith.

2. Automatic tuning apparatus including a rocker pivotally mounted about a given axis to drive a tuning device, and an actuator having laterally spaced arm portions movable generally toward points on opposite sides of said axis and adapted to contact a portion of the rocker on one side of said axis to actuate, the contacted portion of the rocker generally in the direction of movement of the arm portion first contacting it, but always moving the rocker to the same position with both spaced arm portions engaging the rocker, and means for manually operating said actuator, said actuator being shaped to have its mid portion prolecttoward the rocker and to recede outwardly therefrom in such manner that the projecting portion will initially turn the rocker to such a position that the laterally spaced arms of the actuator may readily turn it to the predetermined position.

3. Automatic tuning apparatus including a shaft adapted to drive a tuning device, a rocker on the shaft extending in two directions therefrom, an actuator having laterally spaced arm portions adapted to engage the two extending portions of therocker and to actuate it always to the same position and turn the shaft therewith, and means for .manually operating said actuator, and supporting means other than pivotal means for slidably supporting said operating means, said actuator being shaped to have its mid portion project toward the rocker andv to recede outwardly therefrom in such manner that the. projecting portion will initially turn the roclier to such a position that the laterally spaced arms of the actuator may readily turn it to the predetermined position. v

4. Automatic tuning apparatus including a shaft adapted togdrive'a tuning device, a rocker on the shaft extending in two directions therefrom, an actuator having spaced arm portions adapted to engage the two extending portions of the rocker and to actuate it always to the same position to turn the shaft to a position corresponding with the position of the rocker on the shaft, means for manually operating said actuator, said actuator including a bifurcated slide straddling the shaft, and bushing means mounted on said shaft retaining said rockerin a position for engaging said spaced arm portions, said bushing means being grooved for receiving said bifurcated slide in guiding engagement there with.

5. Tuning apparatus for a radio receiver ineluding in combination a rotary control assembly having a rotary control member, linearly slidable actuator means for moving said control member including a projecting portion for engaging said control member to initially turn the same, and having a stop portion extending to both sides of the transverse mid portion of said actuator for engaging said control member in stopping tuned position, and frame means supporting said actuator in at least two spaced apart points to slidably support the same for linear movement.

6. Tuning apparatus for a radio receiver including in combination a control member mounted for pivotal movement about a given axis, actuating means including a linearly slidable operating portion, an actuator portion having a pair of control-member-engaging-surfaces extending laterally in opposite directions from a line through the 'axis for said control memher, and having a portion intermediate said engaging surfaces projecting 'toward said control member for engaging the same, with said line through the control member axis passing through the projecting portion, and frame means supporting said actuating means for linear slidable movement of the operating portion.

7. Automatic tuning apparatus including a shaft adapted to drive a tuning device, an actuator having a substantially U-shaped end portion straddling said shaft, with each leg of said U-shaped portion having an engaging portion near one end thereof, said engaging portions being opposite each other, a rocker on said shaft extending radially thereof in opposite directions, said rocker having a cam portion at each end operatively engageable with a 'corresponding one of said engaging portions, said engaging portions on actuation of said actuator moving into engagement'with said cam portions to turn the shaft to a position corresponding with the position of the rocker on the shaft, and a bushing member for positioning said rocker axially of said shaft, said bushing being grooved for receiving said actuator legs in gagement therewith.

8. Tuning apparatus for a radio receiver including in combination rotary control means having a control portion extending radially on opposite sides of the axial center thereof, an actuator for said control means having a finger-en- I each other, means on said rotary control means said control portion to move said control means to a position at which said control portion is engaged by both of said engaging portions.

ALEXANDER W. PLENSLER.

guiding en- 

